1. Field of the Invention
The invention describes a technical teaching which allows significant improvements to be achieved in the area of a controlled inhibition of olefinically unsaturated systems which are reactive via free radicals. More specifically, the invention intends to demonstrate a new approach which enables a deliberate pre-selection to be made of the kind and amount of the free radical-inhibitor(s) employed in said systems for stabilization and to ensure this possibility of a deliberate pre-selection even in cases where the technologies as hitherto known for attaining this object have failed to be successful.
2. Statement of Related Art
The concomitant use of inhibitors in the preparation, storage and processing of free radical-sensitive olefinically unsaturated compounds or systems is common chemical knowledge. The inhibitors or inhibitor systems are intended to prevent the initiation of a free radical-initiated reaction at an undesired time; on the other hand, if said systems are intended to be put into use, the inhibitor action will have to be overcome by a controlled initiation of said free radical-initiated reaction. Depending on the conditions of the production of the olefinically unsaturated compounds and/or of the corresponding systems, on the reactivity of the compounds or molecular moieties involved, on the conditions of storage and eventually on the given conditions of use, difficulties may be encounterd in meeting the broad profile of demands as set for stability control by free radical-inhibitors by means of just one special selected inhibitor or inhibitor system. Accordingly, there may be distinguished between "preparation inhibitors" and "application inhibitors" which may be unlike with respect to kind and/or quantity. Thus, for example, it may be desirable, in the preparation of the reactive systems to employ comparably strong inhibitors and/or comparably increased amounts of inhibitors (preparation inhibitors), whereas the storage and/or processing of the reactive system, then, will only require inhibitor or inhibitor systems (application inhibitors) that are comparably less active with respect to kind and/or quantity thereof. In numerous cases it is possible, comparably without any major problem to exchange the preparation inhibitors for the application inhibitors. As an example, there may be mentioned the distillative purification of substance mixtures containing comparably less volatile inhibitors in admixture with distillable olefinically unsaturated components, so that it will be possible, by means of a distillation to isolate the inhibitor-free olefinically unsaturated compound. The pure product thus recovered can then be admixed in a pre-determinable manner with the application inhibitor.
Nevertheless, practice knows many cases wherein such an easy separation of the substance mixture as primarily obtained in the preparation and comprising the preparation inhibitor and the compound reactive via free radicals is not possible. This may be the case, for example, if a distillative separation of the inhibited substance mixture as primarily obtained cannot be effected, e.g. because the boiling points of the unsaturated components are too high or for other reasons. In these and in comparable cases, usually the preparation inhibitor necessarily will also become the application inhibitor. This linkage often causes undesirable bonds for the technology of the step of the preparation of the free radical-reactive system to the technological requirements of the system, including its inhibitor content in practical use.